Benzene ring modified polythiol epoxy curing agent, preparation method thereof and application of benzene ring modified polythiol epoxy curing agent in epoxy resin adhesive

Abstract

The invention discloses a benzene ring modified polythiol epoxy curing agent, a preparation method thereof and application of the benzene ring modified polythiol epoxy curing agent in an epoxy resin adhesive, and the curing agent is prepared from vinyl-3, 3-bis (p-phenyl glycidyl ether) and tetrakis (3-mercaptopropionic acid) pentaerythritol ester through an addition reaction. The preparation method comprises the following steps: mixing tetrakis (3-mercaptopropionic acid) pentaerythritol ester, vinyl-3, 3-bis (p-phenyl glycidyl ether), ethyl acetate and triethylamine, and reacting for 11-13 hours at the temperature of 60-70 DEG C under the protection of nitrogen; and cooling the reactant to room temperature, and carrying out rotary evaporation to remove the solvent to obtain the colorless, transparent and odorless P (SH) 6-PH curing agent. The curing agent provided by the invention has the advantages of low cost, rapid curing, excellent heat resistance and excellent light transmission, and when the curing agent is applied, the epoxy resin adhesive can be obtained by uniformly mixing the curing agent provided by the invention, epoxy resin and an accelerant; the adhesive is suitable for the fields of aerospace, electronic and electrical appliances, automobile manufacturing and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and specifically to a benzene ring-modified polythiol epoxy curing agent, its preparation method, and its application in epoxy resin adhesives. Background Art

[0002] In cutting-edge fields such as aerospace, electronics, and automotive manufacturing, due to the special use environment, materials are constantly breaking through the temperature resistance limit, posing higher requirements for adhesives. Traditional adhesives are prone to failure in high-temperature environments and are difficult to meet the stringent requirements for reliability and durability in these fields. Therefore, developing high-temperature-resistant modified adhesives that can maintain excellent performance at extreme temperatures has become an important research direction in the field of materials science.

[0003] Polythiol curing agents have been widely used in the fields of adhesives, coatings, etc. due to their high reaction activity and fast curing speed. However, the high-temperature resistance of ordinary polythiol curing agents is poor, which limits their application in high-temperature environments. Generally, chemical means such as introducing high-temperature-resistant structural units (sulfone groups, aromatic rings) can be used to improve the heat resistance of the curing agent by utilizing the rigid structure and thermal stability. Vinyl-3,3-bis(p-phenyl glycidyl ether) is a white solid containing a rigid chain segment of a double benzene ring and an ether bond, which will turn into a colorless liquid when heated. It has low cost, no volatility, good heat resistance and corrosion resistance, and can be used as both an epoxy resin diluent and a chemical modifier. Therefore, how to prepare a high-temperature-resistant modified adhesive that can maintain excellent performance at extreme temperatures using vinyl-3,3-bis(p-phenyl glycidyl ether) is an important research topic of the present invention. Summary of the Invention

[0004] The purpose of the present invention is to address the problem that the high-temperature resistance of current polythiol curing agents is poor, which limits their application in high-temperature environments. The present invention provides a benzene ring-modified polythiol epoxy curing agent, its preparation method, and its application in epoxy resin adhesives. The present invention uses vinyl-3,3-bis(p-phenyl glycidyl ether) as a chain extender, and utilizes the epoxy group and double bond in its molecule to undergo an addition reaction with pentaerythritol tetra(3-mercaptopropionate) to synthesize a new curing agent, and uses this curing agent in epoxy resin adhesives.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention provides a benzene ring-modified polythiol epoxy curing agent, which is prepared by an addition reaction of vinyl-3,3-bis(p-phenyl glycidyl ether) and pentaerythritol tetra(3-mercaptopropionate), and the molecular structure of the curing agent is shown in the following formula:

[0007]

[0008] The viscosity of the curing agent of the present invention at 25°C is 30000 mPa·s, and the mercapto value is 0.46 mol / 100 g.

[0009] The present invention also provides a preparation method of a benzene ring-modified polythiol epoxy curing agent, which includes the following steps:

[0010] (1) Mix pentaerythritol tetra(3-mercaptopropionate), vinyl-3,3-bis(p-phenyl glycidyl ether), ethyl acetate and triethylamine, and react at 60-70°C for 11-13 h under nitrogen protection. The molar ratio of pentaerythritol tetra(3-mercaptopropionate) to vinyl-3,3-bis(p-phenyl glycidyl ether) is (1-3):1;

[0011] (2) Cool the above reactants to room temperature, and remove the solvent by rotary evaporation to obtain colorless, transparent and odorless P(SH)6-PH, that is, it is obtained.

[0012] Preferably, in the present invention, the molar ratio of pentaerythritol tetra(3-mercaptopropionate) to vinyl-3,3-bis(p-phenyl glycidyl ether) is 2:1.

[0013] Preferably, the epoxy resin adhesive in the present invention includes a curing agent, epoxy resin E-51 and a promoter.

[0014] Preferably, in the present invention, the mass ratio of epoxy resin to curing agent is 1:1.1.

[0015] Preferably, in the present invention, when the promoter is DMP-30, the addition amount is 3 wt%; when the promoter is DBU, the addition amount is 0.5 wt%.

[0016] In the present invention, the tensile shear strength of the epoxy resin adhesive for Q235 steel is 23.46 MPa, the mass loss rate is 5%, the decomposition temperature of the modified mercaptan is 328°C, the maximum transmittance is 97%, and the yellowing index is 2.58 when irradiated with UV for 32 h.

[0017] In the present invention, the low-temperature bonding properties of the epoxy resin adhesive at -20°C, 5°C and 25°C for 24 h are 12.00 MPa, 14.91 MPa and 18.56 MPa respectively.

[0018] The advantages of the curing agent of the present invention are low preparation cost, fast curing, low temperature resistance, yellowing resistance, excellent heat resistance and light transmittance, and are suitable for adhesives and coatings in the fields of aerospace, electronic appliances, automobile manufacturing, etc. Description of the Drawings

[0020] Figure 1 It is the infrared spectrum diagram of P(SH)6-PH prepared in Example 1;

[0021] Figure 2 1H NMR spectrum of P(SH)6-PH prepared for Example 1;

[0022] Figure 3 Variation curve of gel time of adhesive with different accelerators and their contents when the mass ratio of epoxy resin to P(SH)6-PH curing agent is 1:1.1;

[0023] Figure 4 Effect of accelerator content on tensile shear strength of adhesive when the mass ratio of epoxy resin to curing agent P(SH)6-PH is 1:1.1;

[0024] Figure 5 Effect of different accelerators on hardness of adhesive;

[0025] Figure 6 Effect of different accelerators on tensile strength and elongation at break of adhesive;

[0026] Figure 7 Thermogravimetric analysis of adhesive;

[0027] Figure 8 UV-Vis scanning diagrams of different accelerators;

[0028] Figure 9 Low-temperature bonding performance of adhesive when the accelerators are DMP-30 and DBU. Detailed implementation manners

[0029] For better explaining the present invention and facilitating understanding of its technical solutions, the present invention will be further elaborated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments of the present invention are only for illustrative purposes and are not intended to limit the present invention.

[0030] Example 1

[0031] A preparation method of a benzene ring-modified polythiol epoxy curing agent in this example. Weigh 97.74 g (0.2 mol) of pentaerythritol tetra(3-mercaptopropionate), 33.82 g (0.1 mol) of vinyl-3,3-bis(p-phenylene glycidyl ether), 100 mL of ethyl acetate and 0.3 g of Et3N (0.3 wt%) and add them into a three-necked flask. Under nitrogen protection, react at 65 °C for 12 h, cool to room temperature, and rotary evaporate to remove the solvent ethyl acetate to obtain colorless, transparent and odorless P(SH)6-PH. The reaction equation is as follows:

[0032]

[0033] The P(SH)6-PH curing agent prepared in this example was tested by infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy. Please refer to Appendix Figure 1 and Appendix Figure 2 . It can be seen from Figure 1 that the characteristic peak of -OH generated after the reaction is at 3503 cm -1 , the characteristic peak of -SH of pentaerythritol tetra(3-mercaptopropionate) is at 2570 cm -1 , the characteristic peak of C=O is at 1740 cm -1 , the characteristic peak of S-C is at 1033 cm -1 . There is no C=C characteristic peak at 1680 - 1620 cm -1 for the product after the modification reaction. The characteristic peak of the unreacted epoxy group is at 915 cm -1 , and the characteristic peak of the p-phenyl group is at 830 cm -1 , indicating that the modified polythiol P(SH)6-PH was successfully synthesized. Figure 2 The nuclear magnetic resonance hydrogen spectrum of

[0034] also confirms this result. Among them, the chemical shift parameter δ = 1.6 is the peak at position 5 connected to the epoxy group, the terminal -SH peak, the -OH peak generated after the reaction, and the methylene peak of -SCH2CH2-CH- far from S; δ = 2.66–2.82 is the -CH2- peak near the S atom other than C=O and the -CH2- peak on the epoxy group; δ = 4.07–4.17 comes from the -CH2- peak surrounded by the ester group, the -CH- and -CH2- peaks of HO-CH-CH2-O-, the -CH- peak of -SCH2CH2-CH-, and the methylene peak of -O-CH2-CH-; δ = 6.78 - 7.12 comes from the -CH peak on the benzene ring. The viscosity of the P(SH)6-PH curing agent prepared in this example was measured by a viscometer. At 25 °C, the viscosity of the modified polythiol P(SH)6-PH curing agent in this example was 30000 mPa·s, which was 77 times higher than that of the unmodified polythiol curing agent. This is mainly because the double bond in the vinyl-3,3-bis(p-phenyl glycidyl ether) molecule reacted with the mercapto group in the original unmodified polythiol curing agent molecule under the catalysis of triethylamine. At the same time, the epoxy group of vinyl-3,3-bis(p-phenyl glycidyl ether) reacted with the mercapto group to open the ring, resulting in the growth of the polythiol curing agent molecular chain, the introduction of a benzene ring structure in the molecular structure, an increase in the mercapto content, and a larger relative molecular mass, which greatly increased the viscosity of the modified polythiol curing agent. Due to the significant increase in the viscosity of P(SH)6-PH, although curing can be quickly completed at room temperature or low temperature, its high viscosity makes it difficult to use and pour out. This may be due to the fact that in the molecular design, there are two polythiol molecules in the molecular structure of the curing agent P(SH)6-PH, and the too long molecular chain leads to a large intermolecular force and crosslinking density, resulting in a high viscosity.

[0035] The mercapto value of the P(SH)6-PH curing agent prepared in the example was measured, and the mercapto value of the P(SH)6-PH curing agent was measured to be 0.46 mol / 100 g, which is close to the theoretical mercapto value of 0.456 mol / 100 g.

[0036] The double bond content of the P(SH)6-PH curing agent prepared in the example was measured. The percentage of double bond content in P(SH)6-PH was less than 0.2%. The test results of the double bond content indicate that the double bonds in the vinyl-3,3-bis(p-phenyl glycidyl ether) raw material have basically reacted completely.

[0037] Since the feeding ratio of pentaerythritol tetra(3-mercaptopropionate) to vinyl-3,3-bis(p-phenyl glycidyl ether) is 2:1, therefore, after the double bonds have reacted completely, a nucleophilic addition reaction will occur between the mercapto groups of half of the pentaerythritol tetra(3-mercaptopropionate) and the epoxy groups. Therefore, we can further determine whether the reaction has proceeded completely by measuring the epoxy value. The most commonly used method for measuring the epoxy value is the hydrochloric acid–acetone method. The principle of this method is to use excessive hydrogen chloride to react with the epoxy groups, and then titrate the remaining hydrogen chloride with a standard sodium hydroxide solution to calculate the epoxy value.

[0038] The epoxy value of the reaction product P(SH)6-PH was measured and calculated by the above method. The epoxy value of P(SH)6-PH was 0.0767 mol / 100 g. Compared with the theoretical epoxy value of 0.076 mol / 100 g of the reaction product P(SH)6-PH, the error was about 0.8%. This indicates that the reaction between vinyl-3,3-bis(p-phenyl glycidyl ether) and the raw material pentaerythritol tetra(3-mercaptopropionate) has basically proceeded completely.

[0039] Example 2

[0040] Regarding the application of a benzene ring-modified polythiol epoxy curing agent in this example in an epoxy resin adhesive, the P(SH)6-PH curing agent prepared in Example 1 and E-51 epoxy resin were used as raw materials, and 3 wt% of accelerator DMP-30 was added. When in use, it was quickly stirred and mixed evenly to obtain the epoxy resin adhesive.

[0041] Under the conditions of 25°C and the content of accelerator DMP-30 being 3 wt%, the effects of different mass ratios of epoxy resin / curing agent P(SH)6-PH on the gel time and tensile shear strength of the curing system of the epoxy resin adhesive in this example were studied.

[0042] Table 1 Different mass ratios of epoxy resin / curing agent P(SH)6-PH

[0043]

[0044] As can be seen from Table 1, as the mass ratio of epoxy resin / curing agent P(SH)6-PH increases, the gel time of this curing system shows a trend of first decreasing and then increasing, but the amplitude of increase and decrease is not large. The gel time is the shortest when the mass ratio is 1:1.1. When the mass ratio continues to increase, the gel time shows a slight increase. Generally speaking, the influence of the epoxy resin mass ratio on the gel time of the curing system is not very obvious. Secondly, when the mass ratio of epoxy resin / modified polythiol curing agent ranges from 1:0.5, 1:0.8, 1:1 to 1:1.1, the tensile shear strength of the cured product shows a linear upward trend and reaches 23.46 MPa at a ratio of 1:1.1. When the ratio of the modified polythiol curing agent P(SH)6-PH continues to increase, the tensile shear strength drops linearly. Thus, it can be obtained that the dosage ratio of epoxy resin has a great influence on the bonding strength of the adhesive. Through the calculation of epoxy value and mercapto value, the optimal ratio of epoxy resin to the modified polythiol curing agent P(SH)6-PH is 1:1.1, which is consistent with the experimental results.

[0045] As can be obtained from the above table, epoxy resin and curing agent P(SH)6-PH usually have a shorter gel time and higher tensile shear strength at the optimal theoretical ratio. This is mainly because when the mercapto value and epoxy value of the two-component epoxy resin adhesive system are equivalent, the curing reaction is relatively complete, which increases the reaction rate of the system and the crosslinking degree of the product. Summarizing the above data, it can be known that the optimal usage ratio of epoxy resin to P(SH)6-PH curing agent is 1:1.1.

[0046] Since the molecular chain becomes longer after the chain extension of vinyl-3,3-bis(p-phenyl glycidyl ether) to the polythiol curing agent, and at the same time, non-polar benzene ring groups are introduced into the molecule, increasing the rigidity of the polythiol molecule, and the number of mercapto groups in a single modified polythiol molecule increases, the compatibility between the curing agent and epoxy resin is better, making the curing reaction more complete and the crosslinking density increase, thus greatly enhancing the bonding performance of the adhesive.

[0047] To verify the influence of different accelerators and their contents on the adhesive system, DMP-30 and DBU are selected as accelerators. Attached Figure 3 is the change curve of the gel time of the adhesive with different accelerators and their contents when the mass ratio of epoxy resin to P(SH)6-PH curing agent is 1:1.1. From Figure 3 it can be seen that when the accelerator is DMP-30 and the dosage is 1%, the gel time of the curing system is relatively long and it takes 1020 s to complete curing. When the dosage of the accelerator increases to 3%, the gel time is greatly shortened to 192 s. From Figure 3As can be seen, when the accelerator is DBU and the dosage is 0.1%, the gel time of the curing system is relatively long, and it takes 1500 s to complete curing. When the dosage of the accelerator increases to 0.3% and 0.4%, the gel time is significantly shortened. When the content is 0.4%, the gel time is 300 s. When the content of the two accelerators continues to increase, the catalytic effect is no longer obvious.

[0048] Attachment Figure 4 shows the effect of accelerator content on the tensile shear strength of the adhesive when the mass ratio of epoxy resin to curing agent P(SH)6-PH is 1:1.1. From Figure 4 it can be seen that when the accelerator is DMP-30 and the content is low, the tensile shear strength of the cured product is small; when the accelerator content is 3%, the tensile shear strength of the cured product reaches the maximum value of 23.46 MPa. From Figure 4 it can be seen that when the accelerator is DBU and the content is low, the tensile shear strength of the cured product is small; when the accelerator content is 0.5%, the tensile shear strength of the cured product reaches the maximum value of 20.548 MPa. When the content of the two accelerators continues to increase, the tensile shear strength of the cured product begins to decline again.

[0049] In summary, in the epoxy resin adhesive, when using the curing agent P(SH)6-PH, the optimal mass fraction of the accelerator DMP-30 is 3%, and the optimal mass fraction of the accelerator DBU is 0.5%.

[0050] This example also studied the effect of accelerator type on the mechanical properties of the curing system of the adhesive. Attachment Figure 5 shows the effect of different accelerators on the hardness of the adhesive under the optimal accelerator content (the mass ratio of epoxy resin to curing agent P(SH)6-PH is 1:1.1). As can be seen from the figure, when the accelerator is DMP-30, the hardness of the cured product is 82; when the accelerator is DBU, the hardness of the cured product is 75. This shows that DMP-30 can better promote the complete curing of the curing system because the number of mercapto groups in a single molecule increases after modification, making it more sensitive to the accelerator. When using DBU, the reaction is too fast, resulting in low curing strength, while DMP-30 is more moderate and can better promote the curing of the curing system.

[0051] Attachment Figure 6The effects of different accelerators on the tensile strength and elongation at break of adhesives at the optimal accelerator content (the mass ratio of epoxy resin to curing agent P(SH)6-PH is 1:1.1). It can be seen from the figure that when the accelerator is DMP-30, the tensile strength and elongation at break of the cured product are the largest, which are 66.76 MPa and 49.44%; when the accelerator is DBU, the tensile strength and elongation at break are 50.57 MPa and 33.54%. This further illustrates that the curing effect is the best when DMP-30 is used as the accelerator, because the introduction of non-polar benzene ring groups increases the rigidity of the polythiol molecules, and the number of mercapto groups in a single modified polythiol molecule increases, increasing the crosslinking density, making the adhesive cure completely.

[0052] Example 3

[0053] To verify the water resistance of the curing agent of the present invention, the water absorption rates of adhesives prepared with different accelerators were tested (G1 and G2 are the sample weights before and after water absorption respectively), and the results are shown in Table 2. The water absorption rates of the modified cured products have all decreased. Especially when the accelerator used is DMP-30, it is 0.706%, and the water absorption rate has increased by 53.977% compared with that before modification. This is because the number of reaction sites of polythiol after modification has increased from 4 to 6. Under the condition of a suitable accelerator, the crosslinking density of the adhesive increases, the cured product is more dense, and water is not easily permeated inside, ensuring the stability and weather resistance of the adhesive, and it is consistent with the test conclusions of contact angle and surface energy.

[0054] Table 2 Water Absorption Rates of Different Accelerators

[0055]

[0056] The contact angle is an important basis for judging the wettability of materials. The larger the contact angle between the material and water, the better the hydrophobicity. As shown in Table 3 below, the contact angle when the accelerator is DMP-30 is 85.496° which is greater than the contact angle of 75.740° when the accelerator is DBU. This shows that the curing effect of DMP-30 is better than that of DBU. This is because the alkalinity of DBU is too strong and the reaction is violent, resulting in pores in the cured product, so the contact angle is small and the hydrophobicity is poor.

[0057] Table 3 Effects of Different Accelerators on Contact Angle

[0058]

[0059] Example 4

[0060] To verify the high-temperature resistance of the curing agent of the present invention, the adhesive (P(SH)6-PH) prepared in Example 2 and the adhesive prepared with unmodified thiol curing agent (P(SH)4) were respectively subjected to thermogravimetric analysis tests. See AppendixFigure 7 , as can be seen from the figure, as the temperature rises, the mass of the adhesive rapidly decreases in the temperature range of 350-450 °C. This is because the macromolecular network of the adhesive is broken by heat, generating small molecule volatile products. The mass of the cured coating slowly decreases after 450 °C, corresponding to the further thermal degradation of the char formed in the first stage. When the accelerator is DMP-30 and the mass loss rate of the adhesive is 5%, the decomposition temperature of the unmodified thiol is 248 °C, and that of the modified thiol is 328 °C. When the mass loss rate is 10%, the decomposition temperature of the unmodified thiol is 276 °C, and that of the modified thiol is 345 °C. The rapid weight loss point of the unmodified thiol is 267 °C, and that of the modified thiol is 343 °C, which is significantly increased by 76 °C, indicating that the introduced phenyl rigid group can effectively improve the thermal stability of the adhesive and enhance its heat resistance.

[0061] This example also tested the effect of different accelerators on the transmittance (sample thickness is 0.5 mm) of the adhesive when formulated with the optimal content using a WFZ UV-4802H ultraviolet spectrophotometer produced by Unico (Shanghai) Instrument Co., Ltd. See the appendix Figure 8 , and the measured results are shown in Table 4. It can be seen from the experimental results that the transmittance can reach 96% when the accelerators are DMP-30 and DBU, which is greater than the transmittance of the existing technology that also introduces aromatic rings. The transmittance of the transparent poly(naphthalate) film disclosed in the prior art is 88.4%. This is because the introduced benzene ring has high refractive index and regular molecular structure, which can promote the compatibility between the hard and soft segments, resulting in high optical transparency. Also, the longer the UV cut-off wavelength, the more easily it is eroded by ultraviolet light, and the shorter the cut-off wavelength, the more stable the material is under ultraviolet light. The cut-off wavelength of the DMP-30 accelerator is relatively large, at 358 nm, indicating that the presence of DMP-30 is not stable under the action of ultraviolet light. This may be because the primary amine of DMP-30 easily absorbs the energy of ultraviolet light under natural light and is oxidized and decomposed into azo groups and oxidized azo groups under the action of O2. In summary, when the accelerator is DBU, the stability of the cured adhesive is the best and the transmittance is excellent.

[0062] Table 4 UV-visible light scanning results of different accelerators

[0063]

[0064] The UV yellowing resistance test was carried out for different times using the YI01 yellow index meter of Qingdao Keruide Instrument Co., Ltd. when the accelerator was DBU. The yellowing index is used to characterize the degree of yellowing of materials under the influence of light, heat or other environmental factors. It is an important quality parameter, especially in the field of transparent materials, reflecting the color change of materials due to aging under natural light or ultraviolet irradiation. The larger the yellowing index, the lower the yellowing resistance performance. The specific results are shown in Table 5. The yellowing indices corresponding to 8h, 24h and 32h of UV irradiation are 1.34, 2.29 and 2.58 respectively, and the color of the test pattern has basically not changed, indicating that the adhesive is very stable and has good yellowing resistance performance.

[0065] Table 5 Yellowing test results when the accelerator is DBU

[0066]

[0067] Example 5

[0068] In this example, the bonding performance of the adhesive was tested. The adhesive used the optimal specific ratio as shown in Table 6 below. The comprehensive performance was higher when the accelerator was DMP-30, and the optical performance was better when the accelerator was DBU. Therefore, different accelerators can be selected according to the required performance.

[0069] Table 6 Optimal specific formula

[0070]

[0071] When the accelerator used was DMP-30, the low-temperature bonding performance of the adhesive was studied, and the results are as Figure 9 shown in a. It can be seen from the figure that within 24h, the bonding performance at 3 temperatures showed an overall upward trend. It had a high tensile shear strength within 3h, and the highest tensile shear strengths were 18.56MPa, 14.91MPa and 12.00MPa respectively. The bonding performance at 5℃ could reach 80.32% of that at 25℃, and the bonding performance at -20℃ could reach 80.52% of that at 5℃ and 64.68% of that at 25℃.

[0072] When the accelerator used was DBU, the results are as Figure 9As shown in Figure b. The upward trend within 24 h is the same as that when the accelerator used is DMP-30, and the maximum tensile shear strengths are 16.55 MPa, 13.63 MPa, and 11.28 MPa respectively. The bonding performance at 5°C can reach 82.36% of that at 25°C, and the bonding performance at -20°C can reach 82.76% of that at 5°C and 68.16% of that at 25°C. However, the tensile shear strengths when the accelerator is DBU are all lower than those when the accelerator is DMP-30. It shows that the prepared adhesive has better low-temperature bonding performance when the accelerator is DMP-30.

[0073] Table 7 Effects of different accelerators on the tensile shear strengths of copper and aluminum with different materials

[0074]

[0075] To increase the application range of the adhesive, the tensile shear strengths of copper and aluminum with different materials were tested at 25°C when the accelerators were DMP-30 and DBU. As can be seen from Table 7 above, the tensile shear strengths of copper and aluminum with different materials when the accelerator is DMP-30 are 14.58 MPa and 13.56 MPa respectively; the tensile shear strengths of copper and aluminum with different materials measured when the accelerator is DBU are 13.78 MPa and 12.86 MPa respectively. When Q235 steel is used as the lap joint material, according to the national standard GB / T 13477.8–2017, the tensile shear strengths of the samples after being cured at room temperature and then treated at 90°C for 1 h and immersed in water for 7 d were tested respectively. When the accelerator is DMP-30, they are 27.90 MPa and 21.16 MPa respectively, and the bonding performance is improved by 18.89% after high-temperature treatment. When the accelerator is DBU, they are 18.33 MPa and 16.27 MPa respectively, both of which decrease. In summary, the bonding strength when using DMP-30 is generally greater than that when using DBU.

[0076] The above description is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A benzene ring modified polythiol epoxy curing agent, characterized in that, The curing agent is prepared by an addition reaction of vinyl-3,3-bis(p-phenyl glycidyl ether) and pentaerythritol tetrakis(3-mercaptopropionate), and the molecular structure of the curing agent is shown in the following formula: 。 2. The poly(thiol)-modified epoxy curing agent with a benzene ring according to claim 1, wherein, The viscosity of the curing agent at 25 °C is 30000 mPa·s, and the mercapto value is 0.46 mol / 100 g.

3. The preparation method of a benzene ring modified polythiol epoxy curing agent according to claim 1 or 2, characterized in that, It includes the following steps: (1) Mix pentaerythritol tetrakis(3-mercaptopropionate), vinyl-3,3-bis(p-phenyl glycidyl ether), ethyl acetate and triethylamine, and react at 60-70 °C for 11-13 h under nitrogen protection. The molar ratio of pentaerythritol tetrakis(3-mercaptopropionate) to vinyl-3,3-bis(p-phenyl glycidyl ether) is (1-3):1; (2) Cool the above reactants to room temperature, and remove the solvent by rotary evaporation to obtain colorless, transparent and odorless P(SH)6-PH, thus obtaining the product.

4. The preparation method of a benzene ring modified polythiol epoxy curing agent according to claim 3, characterized in that, The molar ratio of pentaerythritol tetrakis(3-mercaptopropionate) to vinyl-3,3-bis(p-phenyl glycidyl ether) is 2:

1.

5. Use of a benzene ring modified polythiol epoxy curing agent as described in claim 1 or 2 in the preparation of an epoxy resin adhesive, characterized in that, The epoxy resin adhesive includes a curing agent, an epoxy resin and an accelerator.

6. Use of a benzene ring-modified polythiol epoxy curing agent according to claim 5 in the preparation of an epoxy resin adhesive, characterized in that, The mass ratio of the epoxy resin to the curing agent is 1:1.

1.

7. Use of a benzene ring-modified polythiol epoxy curing agent according to claim 5 in the preparation of an epoxy resin adhesive, characterized in that, When the accelerator is DMP-30, the addition amount is 3 wt%; when the accelerator is DBU, the addition amount is 0.5 wt%.

8. Use of a benzene ring modified polythiol epoxy curing agent according to claim 5 in the preparation of an epoxy resin adhesive, characterized in that, The tensile shear strength of the epoxy resin adhesive to Q235 steel is 23.46 MPa, when the mass loss rate is 5%, the decomposition temperature of the modified mercaptan is 328 °C, the maximum transmittance is 97%, and the yellowing index is 2.58 after UV irradiation for 32 h.

9. Use of a benzene ring-modified polythiol epoxy curing agent according to claim 5 in the preparation of an epoxy resin adhesive, characterized in that, The low-temperature bonding properties of the epoxy resin adhesive at -20 °C, 5 °C and 25 °C for 24 h are 12.00 MPa, 14.91 MPa and 18.56 MPa respectively.

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